1). Field of the Invention
This invention relates to an electronic package having a folded, flexible substrate, and to a method of constructing such an electronic package.
2). Discussion of Related Art
Integrated circuits are usually manufactured on semiconductor wafers that are subsequently singulated into individual dies. Such a die may be extremely thin, often less than 100 microns, and is subsequently mounted to a package substrate for purposes of structural integrity. The package substrate also has conductors in the form of traces thereon, metal lines therein and/or vias therein to provide electric interconnection to other devices, often other integrated circuits on other dies.
In order to save space in x and y, it is often required to stack more than one die on top of one another in a z-direction, with the integrated circuits of the dies interconnected with one another. Two dies can, for example, be mounted to a flexible substrate, and the flexible substrate be folded into position such that the dies are above one another. It may also be possible to stack more than two dies on top of one another by folding the flexible substrate at more than one location.
Subsequent integrated circuits in such a stack are interconnected by conductors in the form of traces that run on the flexible substrate across a fold region between the integrated circuits. All the traces run across the fold region. The width of the fold region from a front to a rear side of the flexible substrate thus limits the number of electrical interconnections that can be made.